This invention relates generally to touchscreen systems and more particularly to resistive touchscreen systems.
Resistive touchscreens are used for many applications, including small hand-held applications such as mobile phones and personal digital assistants. When a user touches the resistive touchscreen with two fingers, creating two touch points or dual touch, conventional systems report a single point somewhere between the two touch points as the selected point. In some systems, the transition to a multiple touch state may be detected by a sudden shift in measured coordinates from the first location to a new location. However, an ambiguity may arise between whether a single touch occurred that simply moved rapidly to a different location and whether a multiple touch state occurred.
In another conventional system, sheet bias current or bias load resistance is utilized to indicate a transition from a one touch state to a two or more touch state. The system identifies four corners of a rectangle that is located about the reported single point, but the system is unable to determine which of two opposite corners of the rectangle constitute the true touch coordinates. Also, the system is unable to determine whether more than two actual touches are present.
The identification of the locations of two simultaneous touches is useful in various applications, for example to interact with data being displayed, such as graphics and photos, or with programs, such as when playing music. For example, the ability to use two simultaneous touches to accomplish two-finger gestures such as zoom and rotate would increase the interactive capability the user has with resistive touchscreen systems.
Hence, a need exists for touchscreen systems and methods that are able to detect and identify locations of two simultaneous touches.